WASHINGTON -- Subway and commuter train riders must take a greater role in their own security to help thwart a London-style transit attack in the United States, big-city officials said Tuesday.

Transit security officials from New York City, Los Angeles and Washington focused on low-tech solutions, such as asking the public and transit employees to be on guard for suspicious behavior.

"The most important technology that is out there, right there today, is the human element," said William Morange, head of security for New York's Metropolitan Transportation Authority, which operates the city's subways, buses, and commuter trains.

After the hearing before the House Homeland Security subcommittee on emergency preparedness, science and technology, the head of emergency response for the Los Angeles transit system said he believed a London-style terror attack was "inevitable."

"I and my colleagues already believe that terror cells are here," said Paul Lennon of the Los Angeles County Metropolitan Authority.

New York subway and bus riders are being told to look out for passengers with clenched fists, or who are sweating profusely, or reek of excessive cologne -- all possible indicators of a suicide bomber.

"It's very important that our customers and our employees are fully made aware of their surroundings, and that's something that falls on us," Morange told the panel.